The invention relates generally to covers for the access holes of hydraulic tanks and, more specifically, to a hydraulic tank access cover that has a self-centering and anti-rotation feature.
Mobile construction equipment use hydraulic systems for many uses such as ground drives, hydraulic cylinder activation and hydraulic motor power. These hydraulic systems typically operate at high pressure making them very sensitive to contamination. The hydraulic reservoirs used in these systems need to be thoroughly cleaned before filling with hydraulic oil, otherwise severe contamination can result in excessive pump wear, valve sticking, cylinder scoring, seal tearing, and ultimately total system failure. Having an access hole to be able to clean out the tank before use or even after a system failure has happened can prevent costly future failures.
Hydraulic tank access holes need to be able to be sealed completely such that they do not leak hydraulic oil even when under a given pressure load. Common in the industry are sealing systems which include welding a tapped flange around the hole with blind tapped holes that can hold a gasket and lid bolted down. A second common method is to weld nuts on the underside of the tank surface around the perimeter of the hole to bolt down a lid. Still another form is an outer cover that bolts through the center to a threaded receptacle bolted inside the tank to a gusset or baffle that is welding across the center of the hole inside the tank. All of these methods require expensive machined parts, excess fabrication time, and welding to the inside of the tank. The welding process itself generates a very undesirable form of metal contaminates in the form of weld splatter, weld slag, and flaked off mill scale that are extremely hard on hydraulic systems to the point that a new machine will fail as it drives off the assembly line. An access cover that eliminates welding altogether to the tank has a huge advantage in not generating metal contaminates to begin with.